A happy ending to this story: JPL reported yesterday evening that the flipped bit in Voyager 2's flight data system software has been successfully toggled back to its correct value.
Reset commands were beamed up to the spacecraft yesterday, Wed., May 19, and engineering data received today confirm that the reset was successful. The Voyager team will continue monitoring the engineering data, and if the bit remains reset, commands to switch to the science data mode will be beamed up to Voyager 2 on Sat., May 22. Receipt of science data would then resume on Sun., May 23.
Yay for the Voyager 2 mission team!